Shares of Merck & Co. Inc. (MRK) - Get Report moved higher in early trading Wednesday, Oct. 18, after Citi analysts upgraded the stock for to "buy" from "neutral" on strong sales forecasts.

Carrying sales will be Merck's Keytruda drug, used in immunotherapy treatment for cancer. Citi analysts increased their peak sales forecast for Keytruda to $16 billion from $9 billion. Analysts added that Merck's Keytruda success "outperformed [their] initial expectations," as Merck had previously been weak in the oncology business.

Citi added that the "breadth and depth" of Merck's clinical trials with Keytruda is promising and offers a "sustained, significant advantage." In the industry, Citi noted, only Bristol-Myers Squibb Co. (BMY) - Get Report can compete with Merck's "intensive focus."

Citi raised its price target for Dow component Merck to $72 from $65, suggesting a 12% upside for the shares from their opening price Wednesday. Merck stock was higher about 1% to $63.85 in early trading Wednesday. This is the first time Citi analysts have rated Merck stock as a buy.

More of What's Trending on TheStreet: